This application claims the priority of German patent application No. 197 27 323.8, filed Jun. 27, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process for the outside-moisture-dependent control of an air conditioner of a motor vehicle equipped with a window wiper system.
It is known to control motor vehicle window wiper systems as a function of the outside moisture, that is, as a function of the air moisture (humidity) of the exterior space from which air is taken in for air-conditioning the vehicle interior, particularly for avoiding a fogging-up of vehicle windows. In the situation where an air conditioner is equipped with a refrigerant circulating system having an evaporator and a compressor, when a high air moisture is recognized in the exterior space, for this purpose the air taken in from the exterior space and blown into the interior is cooled in a so-called reheat operation on the cold evaporator. This is so that the moisture condenses on the evaporator and the air is therefore dried and subsequently heated again to the required blow-out temperature. The air current, which is dried in this manner, is then preferably aimed in the direction of the vehicle windows which are to be protected from fogging up, particularly by way of a so-called defroster air duct in the direction of the windshield.
In contrast, in other situations, for example, in the heating operation of the air conditioner, another type of air conditioning and air current guiding is desirable for the air to be blown out into the vehicle interior. Thus, in the heating operation, the air is preferably blown out by way of leg space air ducts and, at most very slightly, by way of the defroster air ducts. Also, when the weather conditions are dry, the amount of air blown in the direction of the vehicle windows does not have to be very large. Hence, the delivery output of a corresponding air blower and thus the noises caused by it can be reduced.
In the case of known simple automatic operating methods of motor vehicle air conditioners, basic ventilation is therefore provided by means of the blower whose intensity is not completely designed according to the least favorable case of a high tendency of the windows to fog up, that is, moist or wet weather, but as a compromise between the various weather conditions, acceptable sound effects and comfortable adjustments with respect to the air output, that is, as a middle course between the normal air-outlet action in the defroster operation, on the one hand, and a pure leg space ventilation, on the other hand. As a result, in the case of these simpler conventional automatic air-conditioning systems, there is the danger that, in the event of unfavorable weather conditions, particularly in the event of rain, in the automatic air-conditioning operating phases, the windows may fog up at least partially and require manual control interventions.
As a remedy, it is known to provide so-called moisture or dew point sensors in order to determine the air moisture or the dew point temperature in the exterior space and, optionally also in the vehicle interior. As a function thereof, the air conditioner is automatically controlled such that a fogging-up of the windows is avoided.
Thus it is known from German Published Patent Application DE 43 16 557 A1 to use the output signal of a sensor system for detecting the degree of thawing or icing on a vehicle window, for example, for the automatic control of a window wiper system, but mainly of an air conditioner. For this purpose, a special sensor system for sensing the degree of thawing or icing and a control of the opening degree of an air flap of the air conditioner and, optionally, also an assembly pertaining to the air conditioner are suggested. This assembly dehumidifies the air to be blown into the interior as a function of the output signal of this sensor system. Other air conditioners with humidity and/or dew point sensor systems and an air-conditioner control as a function of their output signals are disclosed in German Published Patent Application DE 36 24 171 A1 and German Patent Document DE 38 36 559 A1. The implementation of moisture and dew point sensors is connected with corresponding increased expenditures.
For motor vehicles which have a window wiper system, as in particular virtually all of today's automobiles, it is known to provide a manually operable window wiper switch which, in a corresponding switch position, emits a window wiper activation signal which causes a pertaining window wiper control to activate the window wipers. Furthermore, window wiper systems with an automatic wiper activation are known which have a so-called rain sensor by which precipitation, particularly rain, can be recognized on the vehicle windows. When the rain sensor detects precipitation, it emits a wiper activation signal which causes the wiper control to carry out an automatic activation of the window wipers.
From German Published Patent Application DE 39 30 853 A1, a process is known for ventilating a vehicle interior using a ventilating device which can be switched between incoming air and circulating air operation as a function of the output signal of a sensor detecting the pollutant content of the outside air. In this case, the sensitivity of the pollutant sensor is set as a function of a one-step or multi-step wiper activation signal emitted by a window wiper switch. In particular, it is provided to set the sensitivity of this sensor lower in the event of the presence of the wiper activation signal while its activation intensity rises. This has the purpose of preventing an unintentional switching to the circulating air operation in the event of a suddenly occurring rain in the summer which could otherwise occur because the used pollutant sensor reacts to the occurring moisture as if pollutants were present.
The present invention is based on the technical problem of providing a process of the above-mentioned type by which, in moist or wet weather, particularly in the event of precipitation, an air conditioner can automatically be controlled at comparatively low costs such that the fogging tendency of the windows which is threatened in these situations will be counteracted.
The present invention solves this problem by providing a process for the outside-moisture-dependent control of an air conditioner of a motor vehicle equipped with a window wiper system. The output of an air blower is controlled as a function of the presence of a window wiper activation signal for reducing the fogging-up of the windows such that, in the event of the presence of a window wiper activation signal, it is operated at a higher basic output level than when no window wiper activation signal is present. Furthermore, the opening ratio of a defroster air duct, as a function of the presence of a window wiper activation signal, is controlled in a manner which reduces the fogging-up of the window such that, in the event of the presence of the window wiper activation signal, it is selected to be larger than in the absence of the window wiper activation signal by an amount defined as a function of the vehicle interior ventilation temperature.
In the case of this process according to the invention, an air blower or a defroster air duct of the air conditioner is controlled in a manner which reduces the fogging-up of the windows as a function of a window wiper activation signal. The wiper activation signal, generated manually or automatically within the widow wiper system of the motor vehicle in the event of occurring precipitation, particularly rain, for the purpose of activating the wipers, is therefore simultaneously used for controlling the concerned air conditioner component such that such fogging-up of the vehicle windows, particularly of the windshield, which threatens particularly in such moist or wet weather, is prevented or at least reduced. The implementation of high-expenditure moisture and/or dew point sensors specifically for the air conditioner can therefore be eliminated. The signal of a rain sensor or of a manually operable window wiper switch can be used as the wiper activation signal.
In a preferred embodiment, the present invention specifically provides a control of the air blower output such that, in the event of the presence of a window wiper activation signal, a higher basic delivery level is selected than when there is no window wiper activation signal. This increases the air delivery output of the air conditioner, specifically in the operating condition with an approximately adjusted vehicle interior temperature.
In the process according to a further preferred embodiment, especially the opening ratio of the defroster air duct in the event of the presence of a wiper activation signal is selected to be larger than when there is no wiper activation signal by an amount which is defined as a function of the vehicle interior ventilation temperature. This, in particular, permits a varying increase of the opening ratio in the event of an occurring wiper activation signal according to the vehicle interior temperature. For example, it may be provided to raise the opening ratio only above a certain ventilating temperature limit value, in which case the amount of the rise, in turn, can be defined to be increasing with a rising ventilation temperature.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.